Joseph bethenqd



RADIOTELEGRAPHIC COUPLING.

APPLICATION man SEPT-2. 1919.

1 ,427, 350, Patented Aug. 29, 1922.

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' Inventor: JOSEPH BETHENOD,

H. 10. Attorney,

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RADIOTELEGRAI P HIC COUPLING.

Application filed September 2, 1919. Serial No. 321,259.

T 0 all whom it may concern Be it known that T, Jos'nrrr BETI-IENOD, a citizen of the French Republic, residing at 10 Rue Auber, Paris, in the Republic of F rance, have invented certain new and useful Improvements in Radiotelegraphic Couplings (for which I have applied for patents in France, March 15 and July 30, 1918), of which the following is a specification.

The invention refers to an improved system of coupling between an antenna (radiotelegraphic) and a high frequency alternating current generator of the type of those susceptible to furnishing, directly, a current of the frequency necessary forthe feeding of the antenna. This system is applicable outside of any combination required by the difference of phase that may exist between the currents engendered in the different notches of the armature and can be perfectly realized with a monophase alternator.

The purpose in view is to avoid, in such a machine, having the insulators stand an exaggerated tension; the means used is to fractionate the winding into several sections by taking the precautions indicated in the manner of the tying of these sections to the antenna so that the machine may not be the seat of internal circulation currents.

The invention will be more easily understood by reference to the annexed drawings on which Fig. 1 represents the fractioning of the winding of the alternator and the manner of tying with the antenna by means of independent coupling transformers; the Figs. 4 and 5 each represent a modification in the mounting of the secondary windings of the transformers; the Figs. 2 and, 3 represent, respectively front and side view, the manner of preferred execution for the independent transformers; Fig. 6 represents the manner of assembly of the various transformers used.

In those radiotelegraphic installations which are provided with high frequency alternators, the use of intermediary transformers between the alternators and the antenna constitutes most frequently a necessity which is obvious. I

The electromotive force of a high frequency alternator is in actual fact generally fixed, by questions of a constructional nature, at a value which is different from that -which the apparent ohmic resistance of the antenna demands inorder. to bring into play the power of this alternator. Furthermore, the high frequency machines hither; to known have only a very small number of conductors per groove (frequently one only) and consequently, the electromotive force can only be modified by steps, by means of couplings of the windings.

One solution for the indirect coupling of the antenna to a high frequency alternator consists in employing a transformer with very reduced magnetic leakages, without making use of capacities in the primary circuit. For this purpose it is possible to use a transformer with a ferro-magnetic core (naturally with] extra thin sheets) similar to those used in commerce. lVith a transformer of this kind however, the only means, if the installation is of great power, for limiting the fatigue tension of the insulators of the armature windings of the alternator consists, at first sight, in groupmg a certain number of equal parts of the said windings in parallel: this would not furnish a satisfactory solution of the problem by reason of the circulatory currents which would be set up inevitably between these parts, regard being had in particular to the air gap which is relatively always very reduced.

In accordance with the present invention (see Figure 1) a better. solution is secured by again dividing up the armature windings into a certain number of parts 0,, C C, but these are insulated from each other electrically, and are connected individually to the primaries of the transformers T T T (which have very reduced magnetic leakages) in equal numbers, the middle points of the partial windings C C C and of the primaries of the transformers T T T being advantageously connected to the earth E. The secondaries of the said transformers are coupled up in series for example, and the whole is connected between the antenna A and the earth It is obvious that this coupling is not indispensable and that a coupling in para].- lel see Fig. 4 (or in series parallel see Fig". 5) of the said windings is likewise possible, the essential point being the magnetic in dependence of the transformers. Of course. an independent impedance may be provided in the secondary circuit in order to complete the regulation. -With regard to the cores of the transformers, particularly if they have to be of ferromagnetic material, they will be advantageously executed in the form of tori, which tori can be in particular obtained by the piling up of extremely thin sheet iron, separated from each other by a suitable layer of some insulator (such as pa er or varnish). It is interesting to note that with a powerful station, the current which circulates between the antenna and the earth is much more intense than that which passes into one of the conductors of the armature of the high frequency alternator, which circumstance is owing to the smallness of the grooves in this machine.

The system of partial transformers above defined may also be acvantageously constituted in the following manner (see Figures 2 and 3).

The secondary windings, if, for example, they are all coupled up in series, become reduced to a simple conductor S, a tube of copper for example, which is itself covered with an insulating tube of paper, balrelite, etc. Upon this tube are strung a certain number of tori I, each of which is obtained by the piling up of rings of thin sheet iron, insulated from each other. Finally, each of these tori l is wound after the manner of a Grannne ring, and these windings P which form the primaries of the partial transformers are connected to the various insulated parts of the armature windings of the alternator, in accordance with what has been said above. All the transformers thus constituted may be arranged (see Fig. 6) in an oil bath or tank B, with natural or forced circulation. The oil may likewise be cooled by the use of a water coil W or any other known method. An apparatus is thus ob tained which is very simple and very easy to insulate. An advantage of the use of tori consists furthermore in this case in the fact that it avoids all induction mutually between two partial adjacent transformers.

f course auxiliary impedences may be interposed if necessary in the partial primary circuits in order to distribute the charge therein as uniformly as possible.

What I claim and desire to secure by Letters Patent of the United States is A radio-telegraphic station comprising, in combination, a high frequency alternator in which the armature winding is divided into several sections not comprising between their ends any direct electric connection, each of these sections being connected didectly to one of the primary windings of a complex of transformers magnetically independent of each other, the central point of each section of the alternator and the central point of each primary winding being earthed and the secondary windings of these transformers being connected in a suitable manner to the transmitting antenna, the number of the transformers being equal to that of the sections of the armature.

In testimony whereof I aflix my signature in presence of two witnesses.

JOSEPH BETHENOD. Witnesses AUroMIr. MoNrEILHEs, CHAS. P. PnnssLY. 

